Hydraulic prop valve

Claim 1

A VALVE FOR A VENTED CHAMBER OF A HYDRAULIC PROP OR JACK HAVING AT LEAST ONE PASSAGE PASSING THROUGH IT COMPRISING VALVE ELEMENTS BIASSED NORMALLY TO CLOSE SAID PASSAGE, A FLEXIBLE DIAPHRAGM HAVING TWO SIDE FACES, SAID DIAPHRAGM BEING SO MOUNTED THAT IT MAY FLEX IN EITHER DIRECTION PERPENDICULAR TO SAID FACES FROM A MID-POSITION IN RESPONSE TO A DIFFERENCE IN THE PRESSURE ACTING ON SAID FACES, SAID DIAPHRAGM BEING CONNECTED TO SAID VALVE ELEMENTS SO THAT THE FLEXURE OF SAID DIAPHRAGM IN EITHER DIRECTION FROM THE MID-POSITION CAUSES ONE OF SAID VALVE ELEMENTS TO BE UNSEATED TO OPEN THE PASSAGE THROUGH THE VALVE; SAID VALVE HAVING SEPARATE INLET AND OUTLET PASSAGES PASSING THROUGH IT, AND A VALVE ELEMENT BEING PROVIDED FOR EACH OF SAID PASSAGES, MOVEMENT OF THE DIAPHRAGM IN ONE DIRECTION FROM THE MID-POSITION CAUSING THE VALVE ELEMENT IN ONE PASSAGE TO BE UNSEATED AND MOVEMENT OF THE DIAPHRAGM IN THE OTHER DIRECTION FROM THE MIDPOSITION CAUSING THE VALVE ELEMENT IN THE OTHER PASSAGE TO BE UNSEATED, THE VALVE ELEMENT IN SAID ONE PASSAGE BEING FORMED BY A TUBE WHICH IS ATTACHED TO THE DIAPHRAGM, SAID TUBE HAVING AN OUTWARDLY EXTENDING LIP WHICH CLOSES SAID ONE PASSAGE, THE BORE OF SAID TUBE PROVIDING A PORTION OF THE OTHER PASSAGE WHICH IS CLOSED BY THE VALVE ELEMENT IN SAID OTHER PASSAGE WHICH IS POSITIONED WITHIN THE TUBE.